Chemical Names and Formulas Unit 3 Chemical Names and Formulas

Homework Read pages 37-39 Finish all of the “atoms” and “ions” WS Element Name and Symbol WS Retest Thursday 12/2 or Friday 12/3 Quiz Dec. 6 and 7 (Monday and Tuesday)

STABILITY At rest, not willing to react A state likely to be found in nature Opposite = reactive or unstable Stable = 8 valence electrons in outer shell = octet rule Stability refers to number of ELECTRONS in outer shell

Cations Formed by metals Number of outer electrons = group number Example: Li and Na both have 1 valence electron How about Mg and Ca?

Formation of ions Sodium has 11 protons and 11 electrons. Sodium loses 1 electron to form a sodium ion

ATOM STABILITY Related to the number of electrons which the atom contains Atoms will try to lose or gain electrons to achieve a noble gas configuration

Noble Gas Rule Whenever an atom is surrounded by the same number of electrons as a noble gas it is very stable.

Anion Formed by non-metals Gain electrons to achieve noble gas configuration Charge of the anion = group# - 8 Example: oxide anion has a charge of 6-8 = 2-

Formation of ions

Anions vs. Cations Anions end in ide Example: bromide, oxide, sulfide bromide anion = Br1- oxide anion = O2- Anion is always larger than the atom from which it was formed

sulfur S S2- sulfide bromine Br Br- bromide iron Fe Fe2+ iron(II) aluminum Al Al3+ aluminum calcium Ca Ca2+ calcium lead Pb Pb2+/Pb4+ lead(II) or lead(IV) cesium Cs Cs+ cesium nitrogen N N3- nitride cobalt Co Co2+/Co3+ cobalt(II) or cobalt(III) fluorine F F- fluoride copper Cu Cu+ copper(I) lithium Li Li+ lithium

Cation Always smaller than the atom from which it was formed Metal + ion Example sodium cation (Na1+) Magnesium ion (Ca2+) http://www.youtube.com/watch?v=QSZ-3wScePM http://www.youtube.com/watch?v=hqbwPxZsgHs

Homework Read pages 40-43 (omit polyatomic ions) Binary ionic compound worksheet 6.4 Ionic Compound worksheet Retest Thursday 12/2 or Friday 12/3 Quiz Dec. 6 and 7 (Monday and Tuesday)

Compounds Two or more different elements combined chemically MOLECULAR versus IONIC

Ionic Compounds Positive cation + negative anion Cation gives electrons Anion accepts electrons Electrically neutral Metal + non-metal Usually solid at room temp.

Naming Ionic Compounds Metal comes first in the name Non-metal – ending changes to ‘ide’ Example: NaCl sodium chloride

Chemical Formula Shows the number and kinds of atoms in the smallest representative unit

Formula Unit Lowest whole number ratio of ions in an ionic compound NaCl NOT Na2Cl2 How is magnesium and chlorine combined to form an ionic compound?

Binary Ionic Compounds Binary – composed of two elements (+) charge must balance (-) charge Net charge = 0 Cation is written first

Writing Formulas for Binary Ionic Compounds Potassium Chloride K+ and Cl- Charge ratio 1:1 KCl

Writing Formulas for Binary Ionic Compounds Calcium Bromide Ca+2 and Br- Charge ratio 2:1 CaBr2

Writing Formulas for Binary Ionic Compounds Use criss cross method Charge on one ion becomes the subscript on the other Reduce to lowest whole number ratio.

Writing Formulas for Binary Ionic Compounds Fe3+ combines with O2- Fe3+ O2- Fe2O3

Writing Formulas for Binary ionic Compounds Ca2+ combines with S2- Ca2+ S2- Ca2S2 Reduces to CaS

Formulas and Names Write formulas from ions Write formulas from names Ba2+, S2- Li+, O2- Ca2+, N3- Cu2+, I- Write formulas from names Sodium iodide Stannous chloride Potassium sulfide Calcium iodide